Synthesis of dihalohydrins and tri- and tetra-substituted olefins

ABSTRACT

A novel synthesis reaction for highly stereospecific tri- and tetra-substituted olefins is described. A single stereoisomer of stable α-halo-α,β-ester is produced in high yield by the reaction of aldehyde or ketone with a trihalogenated compound such as trichloroacetate in the presence of CrCl 2  in a solvent. By varying the amount of CrCl 2  used, the stable dihalohydrin intermediate may be obtained as well.

BACKGROUND

[0001] One embodiment of this invention relates to synthesis of olefins and, in particular, to stereospecific synthesis of tri- and tetra-substituted olefins.

[0002] The highly stereoselective construction of tri- and tetra-substituted olefins is currently one of the most challenging problems in synthetic organic chemistry. Tri- and tetra-substituted olefins are common structural units in almost every class of compounds, particularly natural products. Their synthesis is consequently of great importance to the pharmaceutical, agricultural, and fine chemical industries. However, there are few methods that can do this efficiently, economically, and with high stereoselectivity. Many extant procedures give poor yields, require expensive reagents, have inconvenient reaction conditions, produce undesirable by-products, and afford mixtures of isomers. Since the isomers and by-products may be hard to remove, impart undesirable chemical or physical properties, and have unwanted biological properties, these compounds must be separated by methods that can be costly, difficult to conduct on a large scale, and time consuming.

[0003] The literature provides some examples of methods for the synthesis of tri-substituted olefins. (See Tago et al., Organic Lett., 2:1975-78 (2000); Ishino et al., Bull. Chem. Soc. Jpn., 71:2669-72 (1998); Goumain et al., Synthesis, 6:984 (1999); and Kruper et al., J. Org. Chem., 56:3323-29 (1991)). In addition, some previous examples exist for the synthesis of tetra-substituted olefins, such as α-halo acrylates. (See Takai et al., Bull. Chem.. Soc. Jpn., 53:1698-1702 (1980); Masahira et al., Synth. Commun., 30:863-68 (2000); Terent'ev et al., Russ. Chem. Bull., 48:1121-27 (1999)). However, these methods tend to be inefficient due to lack of stereoselectivity or the need for a multi-step procedure.

[0004] Most frequently, Wittig and Horner-Wadsworth-Emmons (“HWE”) reactions are used in the synthesis of various olefins. (See Wadsworth et al., Org. React., 25:73 (1977); Maryanoff et al., Chem. Rev., 89:863 (1989); and Vedejs et al., Top. Stereochem., 21:1 (1994)). But the construction of tri- and tetra-substituted alkenes is subject to the limitations of variable stereoselectivity, costly reagents, and low yields.

SUMMARY

[0005] One aspect of the current invention relates to an efficient synthesis method for the stereoselective production of tri- and tetra-substituted olefins in high yield. A single stercoisomer of (Z)-α-halo-α,β-unsaturated ester, also known as α-halo-(Z)-acrylate, is produced in a reaction between aldehydes and trihalogenated compounds such as trichloroacetate. Aldehydes in combination with dihalogenated propionates, as well as higher homologs of the dihalogenated propionates with longer carbon chains, also produce stereospecific results. These reactions are carried out in the presence of a reductant, such as 4 CrCl₂ or catalytic CrCl₂, Mn, and chlorotrimethylsilane (“TMSCl”) in a polar solvent, preferably at ambient temperatures and under an inert atmosphere, such as an argon or nitrogen atmosphere. The same method produces tetra-substituted olefins of good stereoselectivity if ketones are used instead of aldehydes. Solvents that can be used for these reactions include tetrahydrofuran (“THF”), dimethylformamide (“DMF”), ethylene glycol dimethyl ether (“DME”), other polar solvents, and a mixture thereof.

[0006] In addition, using 2 equivalents of CrCl₂ rather than 4 produces the intermediate dihalohydrin compound in very high yield. Further conversion of the dihalohydrin to principally one stercoisomer of tri- or tetra-substituted olefin is possible by adding another 2 equivalents of CrCl₂. Thus, in a single step, by varying the amount of CrCl₂, the final product may be either the olefin or the dihalohydrin. The general scheme for this reaction is illustrated below. In this reaction scheme, X may be Cl, Br, F, an alkyl group, or an aryl group. R and R′ may be similar or different and may be alkyl, allyl, aryl, heteroaryl, aliphatic, or cycloaliphatic groups. The trihalogenated compound is illustrated as 1, the intermediate dihalohydrin is 2, and the substituted olefin is 3.

[0007] As an example, remarkably high stereoselectivities are observed when acetophenone and methyl trichloroacetate are used to produce the tetra-substituted olefin in a 75:1 Z/E ratio. In another variation, the transformation of aldehyde to (E)-methacrylate using 2,2-dichloropropionate is unrivaled by conventional reagents for its stereoselectivity (greater than 99% of the (E)-isomer) and yield.

[0008] Although not wanting to be bound by theory, it is likely that the reaction mechanism involves the oxidative addition of Cr(II) into a C—Cl bond via two consecutive single electron transfers and subsequent addition to the aldehyde carbonyl. Subsequent E2-elimination of the resultant Reformatsky-type adduct 2 affords the α-haloacrylate 3. Of the possible anti-periplanar conformations illustrated below, conformer A is favored because it minimizes the steric interactions between the ester and R group. Selective metallation of the chloride furthest from the chromate ester ensures the observed stereochemistry.

[0009] The synthesis of (Z)-halogenated tri- and tetra-substituted olefins is useful in the synthesis of various biologically active products by the method of transition metal mediated cross-coupling. Applications range from the preparation of α-amino acids, heterocycles, polymers, and aziridines to natural products and pharmaceuticals.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

[0010] The results from a panel of representative substrates in the synthesis of tri-substituted olefins, or α-haloacrylates are summarized in Table 1 below. TABLE 1 Synthesis of (Z)-α-Haloacrylates Entry Aldehyde Acrylate 1

X-Cl, R = Me  99 X = F, R = Et  98 2

 99 3

 99 4

100 5

 99 6

 98 7

X = Cl, R = Me  98 X = Br, R = Me  98 X = F, R = Et  98 8

 99 9

 99 10

X = Cl  99 X = Br  98 11

 98 12

 91^(a)

[0011] Specifically, aliphatic aldehyde or secondary aldehyde, stirred with 4 equivalents of commercial CrCl₂ and methyl trichloroacetate at room temperature for 0.5 hours generates the corresponding (Z)-α-halo-α,β-unsaturated ester products shown in Table 1 under entries 1 and 2 respectively. Nuclear magnetic resonance (“NMR”) analysis of the crude reaction mixture does not detect any of the (E)-isomer, indicating better than 99% stereochemical purity. A catalytic CrCl₂ system, utilizing Mn powder to recycle chromium (III) to chromium (II), also produces a good yield of the desired products.

[0012] Illustrated in entries 3, 4, and 5 respectively, condensation of chiral carboxaldehyde, simple benzaldehyde, and cinnamaldehyde produces corresponding tri-substituted olefin compounds in high yield. Furthermore, neither the reaction rate nor yield are significantly influenced by electron donating or withdrawing substituents on the substrates, as shown in entries 7 and 10. The resulting products were present in high yield. The reaction is compatible with a variety of functional groups, including reactive bromine (entry 9), benzyloxy (entry 8), bis-methyleneoxy ether (entry 10), tertiary amine (entry 11) and secondary amine (entry 12). The transformation also proceeds smoothly with methyl tribromoacetate and p-anisaldehyde (entry 7, where X=Br and R=Me). All reaction products are present in high yield.

[0013] The standard stoichiometric reaction also works well for the synthesis of tetra-substituted olefins. Reacting methyl trihaloacetate with ketones gives good yield of the tetra-substituted halo esters in about a 1:5 ratio of (E) to (Z)-stereoisomers, but this ratio varies depending on the substrate. By isolating the alcohol product first by using 2 equivalents of CrCl₂, then treating with an additional 2 equivalents of CrCl₂, the stereochemical ratio may be increased up to 1:16 with some substrates. As a generalized illustration of the tetra-substituted synthetic methodology, results from reactions with different substrates are shown in Table 2 below. The synthesized tetra-substituted olefins, or adducts, are illustrated. TABLE 2 Olefination of ketones Entry Ketone Adduct Yield (%) E/Z 1

95 1/2.5 2

98 1/5^(a) 3

95 1/2.5 4

93 1/5

[0014] As shown in entries 1, 2, 3, and 4 respectively, aliphatic ketone, aromatic ketone, conjugated ketone, and hindered ketone give rise to reaction products in excellent yield after the addition of methyl trihaloacetate. The tetra-substituted olefin of Entry 2 was synthesized at a Z/E ratio of 75:1 when the solvent used was a mixture of THF and DMF in equal parts, while the Z/E ratio of 5:1 was obtained in THF alone.

[0015] Using 2 equivalents of CrCl₂ at a reaction temperature of about 0° C., rather than 2 equivalents of CrCl₂ at about room temperature, allows the isolation of the intermediate dihalohydrin compounds in moderate to good yield as well. The results from a panel of representative substrates in the synthesis of dihalohydrins, or adducts, are summarized in Table 3 below. TABLE 3 Synthesis of dihalohydrin Entry Aldehyde Adduct Yield (%) 1

82 2

65 3

84 4

78 5

75 6

76

[0016] A variety of trihalogenated compounds, in addition to trichloroacetate, may be used to synthesize the substituted olefins, or adducts. As illustrated below in Table 4, these trihalogenated compounds include 2,2,2-trichloroacetamide (entries 1-2), 1,1,1-trichlorotoluene (entries 3-4), and 1,1,1-trichloroacetone (entries 5-6). In addition, entries 7 and 8 show the formation of substituted olefins in good yield with the use of α,β-dichloropropiophenone. TABLE 4 Olefinations using other trihalogenated compounds Entry Aldehyde Chloride Adduct Yield (%) 1

95 2

92 3

95 4

93 5

99 6

99 7

88 8

85

EXAMPLE 1. GENERAL SYNTHESIS OF TRI-SUBSTITUTED OLEFINS

[0017] Methyl trihaloacetate (1 mmol) and aldehyde (1 mmol) in THF (2 mL) were added to a stirring suspension of anhydrous CrCl₂ (4.5 mmol) in THF (8 mL) under argon at ambient temperature. After 0.5 hours, the resultant reddish reaction mixture was quenched with water, extracted three times with ether, and the combined ethereal extracts were evaporated in vacuo. Chromatographic purification on SiO2 resulted in (Z)-α-halo-α,β-unsaturated esters in the yields indicated in Table 1.

EXAMPLE 2. GENERAL SYNTHESIS OF TRI-SUBSTITUTED OLEFINS USING CATALYTIC CHROMIUM

[0018] Methyl trihaloacetate (1 mmol) and aldehyde (1 mmol) in THF (2 mL) were added to a stirring suspension of anhydrous CrCl₂ (50 mol %), Mn power (4 mmol) and TMSCI (6 mmol) in THF (8 mL) under argon at ambient temperature. After 12 hours, the resultant reddish reaction mixture was quenched with water, extracted three times with ether, and the combined ethereal extracts were evaporated in vacuo. Chromatographic purification on SiO₂ resulted in (Z)-α-halo-α,β-unsaturated esters in yields comparable to those indicated in Table 1.

EXAMPLE 3. GENERAL SYNTHESIS OF TETRA-SUBSTITUTED OLEFINS

[0019] Methyl trihaloacetate (1 mmol) and ketone (1 mmol) in THF (2 mL) were added to a stirring suspension of anhydrous CrCl₂ (6 mmol) in THF (8 mL) under argon at ambient temperature. After 2 hours, the resultant reddish reaction mixture was quenched with water, extracted three times with ether, and the combined ethereal extracts were evaporated in vacuo. Chromatographic purification on SiO₂ resulted in (Z)-α-halo-α,β-unsaturated esters in the yields indicated in Table 2.

EXAMPLE 4. GENERAL SYNTHESIS OF DIHALOHYDRINS

[0020] Methyl trihaloacetate (1 mmol) and aldehyde (1 mmol) in THF (2 mL) were added to a stirring suspension of anhydrous CrCl₂ (2.5 mmol) in THF (8 mL) under argon at 0° C. After 6 hours, the resultant reddish reaction mixture was quenched with water, extracted three times with ether, and the combined ethereal extracts were evaporated in vacuo. Chromatographic purification on SiO₂ gave the dihalohydrins, or adducts, shown in Table 3.

EXAMPLE 5. SYNTHESIS OF METHYL 2-CHLORO-5-PHENYLPENT-2(Z)-ENOATE

[0021] In accordance with the general procedure described in Example 1 above, ethyl dibromofluoroacetate and commercial hydrocinnamaldehyde were converted to methyl 2-chloro-5-phenylpent-2(Z)-enoate as an oil in the indicated yield for Entry 1, where X=Cl and R=Me, in Table 1.

[0022] R_(f): 0.75 (15% EtOAc in hexane). ¹H NMR (CDCI₃, 400 MHz): δ2.64-2.72 (m, 2H,—CH₂—), 2.80 (t, 2H, J=7.6 Hz, Ph—CH₂—), 3.81 (s, 3H, CO₂CH₃), 7.01 (t, 1H, J=7.2 Hz), 7.18-7.26 (m, 3H), 7.28-7.34 (m, 2H). ¹³C NMR (CDCI₃, 75 MHz): δ31.20, 33.83, 53.25, 125.23, 126.52, 128.49, 128.75, 140.65, 171.66,163.11. MS: m/z 224 (M⁺), 226 (M⁺+2).

EXAMPLE 6. SYNTHESIS OF METHYL 2-CHLORO-4-PHENYLPENT-2(Z)-ENOATE

[0023] In accordance with the general procedure described in Example 1 above, commercial aliphatic branched aldehyde was converted to methyl 2-chloro-4-phenylpent-2(Z)-enoate as an oil in the indicated yield for Entry 2 in Table 1.

[0024] R_(f): 0.70 (15% EtOAc in hexane). ¹H NMR (CDCI₃, 300 MHz): δ1.44 (d, 3H, J=6.6 Hz, CH₃), 3.81 (s, 3H, CO₂CH₃), 4.35-4.15 (m, 1H), 7.6 (d, 1H, J=9.6 Hz, CH═), 7.20-7.36 (m, 5H). ¹³C NMR (CDCI₃, 75 MHz): δ20.10, 39.75, 53.29, 123.24, 127.13, 127.26, 128.98, 142.92, 146.15, 163.28. MS: m/z 224 (M⁺), 226 (M⁺+2).

EXAMPLE 7. SYNTHESIS OF METHYL 2-CHLORO-3-(2,2-DIMETHYL-[1,3]DIOXOLAN-4(S)-YL)PROP-2(Z)-ENOATE

[0025] In accordance with the general procedure described in Example 1 above, chiral glyceraldehyde was converted to methyl 2-chloro-3-(2,2-dimethyl-[1,3]dioxolan-4(S)-yl)prop-2(Z)-enoate as an oil in the indicated yield for Entry 3 in Table 1.

[0026] R_(f): 0.65 (15% EtOAc in hexane). ¹H NMR (CDCI₃, 300 MHz): δ1.41 (s, 3H, CH₃), 1.46 (s, 3H, CH₃), 3.71 (dd, 1H, J=6.6, 8.1 Hz), 3.85 (s, 3H, CO₂CH₃), 4.30 (dd, 1H, J=6.6, 8.4 Hz), 5.02 (dd, 1H, J=6.6, 13.5 Hz), 7.12 (d, 1H, 6.9 Hz). ¹³C NMR (CDCI₃, 75 MHz): δ25.71, 26.60, 53.53, 68.40, 73.52, 110.44, 125.63, 140.81, 162.33. MS: m/z 220 (M⁺), 222 (M⁺+2).

EXAMPLE 8. SYNTHESIS OF METHYL 2-CHLORO-3-PHENYL-PROP-2(Z)-ENOATE

[0027] In accordance with the general procedure described in Example 1 above, benzaldehyde was converted to methyl 2-chloro-3-phenyl-prop-2(Z)-enoate as an oil in the indicated yield for Entry 4 in Table 1.

[0028] R_(f): 0.70 (15% EtOAc in hexane). ¹H NMR (CDCI₃, 300 MHz): δ3.89 (s, 3H, CO₂CH₃), 7.36-7.48 (m, 3H), 7.80-7.86 (m, 2H), 7.91 (s, 1H, Ph—CH═). ¹³C NMR (CDCI₃, 75 MHz): δ53.55, 121.91, 128.72, 130.44, 130.83, 133.03, 137.42, 164.11. MS: m/z 196 (M⁺), 198 (M⁺+2).

EXAMPLE 9. SYNTHESIS OF METHYL 2-CHLORO-5-PHENYLPENT-ENOATE

[0029] In accordance with the general procedure described in Example 1 above, commercial cinnamaldehyde was converted to methyl 2-chloro-5-phenylpent-2(Z),4(E)-dienoate as an oil in the indicated yield for Entry 5 in Table 1.

[0030] R_(f): 0.72 (15% EtOAc in hexane). ¹H NMR (CDCI₃, 300 MHz): δ3.86 (s, 3H, CO₂CH₃), 7.00 (d, 1H, J=15.9 Hz), 7.19 (dd, 1H, J=10.8, 15.3 Hz), 7.30-7.40 (m, 3H), 7.46-7.54 (m, 2H), 7.62 (d, 1H, J=10.8 Hz). ¹³C NMR (CDCI₃, 75 MHz): δ53.28, 122.3, 123.04, 127.73, 129.05, 129.74, 136.03, 138.23, 142.41, 163.67. MS: m/Z 222 (M⁺), 224 (M⁺+2).

EXAMPLE 10. SYNTHESIS OF METHYL 2-CHLORO-3-(4-ETHYLPHENYL)PROP-2(Z)-ENOATE

[0031] In accordance with the general procedure described in Example 1 above, commercial p-trifluoromethylbenzaldehyde was converted to methyl 2-chloro-3-(4-trifluoromethylphenyl)prop-2(Z)-enoate as an oil in the indicated yield for Entry 6 in Table 1.

[0032] R_(f): 0.73 (15% EtOAc in hexane). ¹H NMR (CDCI₃, 300 MHz): δ3.93 (s, 3H, CO₂CH₃), 7.68 (d, 2H, J=8.4 Hz), 7.91 (d, 2H, J=8.4 Hz), 7.93 (s, 1H). ¹³C NMR (CDCI₃, 75 MHz): δ54.22, 124.84, 126.01, 126.11, 131.27, 136.17, 136.87, 164.04. MS: m/z 264 (M⁺), 266 (M⁺+2).

EXAMPLE 11. SYNTHESIS OF METHYL 2-CHLORO-3-(4-METHOXYPHENYL)PROP-2(Z)-ENOATE

[0033] In accordance with the general procedure described in Example 1 above, ethyl dibromofluoroacetate and commercial p-methoxybenzaldehyde were converted to methyl 2-chloro-3-(4-methoxyphenyl)prop-2(Z)-enoate as an oil in the indicated yield for Entry 7, where X=Cl and R=Me, in Table 1.

[0034] R_(f): 0.68 (15% EtOAc in hexane). ¹H NMR (CDCI₃, 300 MHz): δ3.84 (s, 3H, CO₂CH₃), 3.88 (s, 3H, —OCH₃), 6.94 (d, 2H, J=8.7 Hz), 7.85 (d, 2H, J=8.7 Hz), 7.86 (s, 1H). ¹³C NMR (CDCI₃, 75 MHz): δ53.41, 55.53, 114.18, 119.30, 125.70, 132.91, 137.00,161.34, 164.41. MS: m/z 226 (M⁺), 228 (M⁺+2).

EXAMPLE 12. SYNTHESIS OF METHYL 2-BROMO-3-(4-METHOXYPHENYL)PROP-2(Z)-ENOATE

[0035] In accordance with the general procedure described in Example 1 above, ethyl dibromofluoroacetate and commercial p-methoxybenzaldehyde were converted to methyl 2-bromo-3-(4-methoxyphenyl)prop-2(Z)-enoate as an oil in the indicated yield for Entry 7, where X=Br and R=Me, in Table 1.

[0036] R_(f): 0.69 (15% EtOAc in hexane). ¹H NMR (CDCI₃, 300 MHz): δ3.84 (s, 3H, CO₂CH₃), 3.88 (s, 3H, —OCH₃), 6.94 (d, 2H, J=9.0 Hz), 7.90 (d, 2H, J=9.0 Hz), 8.17 (s, 1H). ¹³C NMR (CDCI₃, 75 MHz): δ53.41, 55.53, 114.18, 119.30, 125.70, 132.91, 137.00, 161.34, 164.41. MS: m/z 226 (M⁺), 228 (M⁺+2).

EXAMPLE 13. SYNTHESIS OF METHYL 2-CHLORO-3-(4-BENZYLOXY-3-METHOXYPHENYL)PROP-2(Z)-ENOATE

[0037] In accordance with the general procedure described in Example 1 above, commercial 4-benzyloxy-3-methoxy-benzaldehyde was converted to methyl 2-chloro-3-(4-benzyloxy-3-methoxyphenyl)prop-2(Z)-enoate as an oil in the indicated yield for Entry 8 in Table 1.

[0038] R_(f): 0.55 (15% EtOAc in hexane). ¹H NMR (CDCI₃, 400 MHz): δ3.89 (s, 3H,—CO₂CH₃), 3.93 (s, 3H, —OCH₃), 5.21 (s, 2H), 6.91 (d, 1H, J=8.4 Hz), 7.28-7.40 (m, 4H), 7.43 (d, 2H, J=7.2 Hz), 7.57 (s, 1H), 7.84 (s, 1H). ¹³C NMR (CDCI₃, 75 MHz): δ53.46,56.19,70.92, 113.16, 113.73, 119.47, 125.42, 126.23, 127.37, 128.23, 128.84, 136.64, 137.15, 149.33, 150.23, 164.35. MS: m/z 332 (M⁺), 334 (M⁺+2).

EXAMPLE 14. SYNTHESIS OF METHYL 2-CHLORO-3-(3-BROMOPHENYL)PROP-2(Z)-ENOATE

[0039] In accordance with the general procedure described in Example 1 above, commercial 3-bromo-benzaldehyde was converted to methyl 2-chloro-3-(3-bromophenyl)prop-2(Z)-enoate as an oil in the indicated yield for Entry 9 in Table 1.

[0040] R_(f): 0.71 (15% EtOAc in hexane). ¹H NMR (CDCI₃, 300 MHz): δ3.91 (s, 3H, CO₂CH₃), 7.30 (t, 1H, J=7.80 Hz), 7.50- 7.55 (m, 1H), 7.70-7.75 (m, 1H), 7.83 (s, 1H), 7.98 (t, 1H, J=1.8 Hz). ¹³C NMR (CDCI₃, 75 MHz): δ53.70, 122.77, 123.40, 129.31, 130.21, 133.24, 133.30, 135.0, 135.76, 163.68. MS: m/z 274 (M⁺), 276 (M⁺+2).

EXAMPLE 15. SYNTHESIS OF METHYL 2-CHLORO-3-(1,3-BENZODIOXOL-5-YL)PROP-2(Z)-ENOATE

[0041] In accordance with the general procedure described in Example 1 above, commercial benzaldehyde with a methylenedioxy group was converted to methyl 2-chloro-3-(1,3-benzodioxol-5-yl)prop-2(Z)-enoate as an oil in the indicated yield for Entry 10 in Table 1, where X=Cl.

[0042] R_(f): 0.65 (15% EtOAc in hexane). ¹H NMR (CDCI₃, 300 MHz): δ3.89 (s, 3H, CO₂CH₃), 6.03 (s, 4H), 6.86 (d, 1H, J=8.4 Hz), 7.27 (dd, 1H, J=1.5,7.2 Hz), 7.59 (d, 1H, J=1.8 Hz), 7.82 (s, 1H). MS: m/z 240 (M⁺), 242 (M⁺+2).

EXAMPLE 16. SYNTHESIS OF METHYL 2-BROMO-3-(1,3-BENZODIOXOL-5-YL)PROP-2(Z)-ENOATE

[0043] In accordance with the general procedure described in Example 1 above, commercial benzaldehyde with a methylenedioxy group was converted to methyl 2-bromo-3-(1,3-benzodioxol-5-yl)prop-2(Z)-enoate as an oil in the indicated yield for Entry 10 in Table 1, where X =Br.

[0044] R_(f): 0.48 (15% EtOAc in hexane). ¹H NMR (300 MHz) δ3.89 (s, 3H), 6.03,(s, 2H), 6.85 (d, 1H, J=8.1 Hz), 7.28-7.32 (m, 1H), 7.65 (d, 1H, J=1.8 Hz), 8.13 (s, 1H); ¹³C NMR (75 MHz) δ53.72, 101.87, 108.56, 109.67, 110.21, 127.28, 140.80, 147.89, 149.65, 164.26; MS m/z 284 (M⁺), 288 (M⁺+2).

EXAMPLE 17. SYNTHESIS OF METHYL 2-CHLORO-3-(4-DIMETHYLAMINOPHENYL)PROP-2(Z)-ENOATE

[0045] In accordance with the general procedure described in Example 1 above, commercial 4-dimethylaminobenzaldehyde was converted to methyl 2-chloro-3-(4-dimethylaminophenyl)prop-2(Z)-enoate as an oil in the indicated yield for Entry 11 in Table 1.

[0046] R_(f): 0.45 (15% EtOAc in hexane). ¹H NMR (CDCI₃, 300 MHz): δ3.04 (s, 6H), 3.87 (s, 3H, CO₂CH₃), 6.68 (d, 2H, J=9.0 Hz), 7.83 (s, 1H), 7.40 (d, 2H, J=9.0 Hz). ¹³C NMR (CDCI₃, 75 MHz): δ40.22, 53.29, 111.54, 116.14, 120.76, 133.11, 137.78, 151.70, 164.98. MS: m/z 239 (M⁺), 241 (M⁺+2).

EXAMPLE 18. SYNTHESIS OF METHYL 2-CHLORO-3-(lH-INDOL-2-YL)PROP-2(Z)-ENOATE

[0047] In accordance with the general procedure described in Example 1 above, commercial indole aldehyde was converted to methyl 2-chloro-3-(1H-indol-2-yl)prop-2(Z)-enoate as an oil in the indicated yield for Entry 12 in Table 1.

[0048] R_(f): 0.35 (15% EtOAc in hexane). ¹H NMR (CDCI₃, 300 MHz): δ3.92 (s, 3H,—CO₂CH₃), 7.20-7.36 (m, 2H), 7.44 (d, 1H, J=7.2 Hz), 7.81 (d, 1H, J=7.5 Hz), 8.31 (s, 1H), 8.32 (d, 1H, J=4.2 Hz), 8.81 (bs, 1H). ¹³C NMR (CDCI₃, 75 MHz): δ53.30,110.97,111.79,117.20,118.60,121.59,123.67, 127.77, 128.76, 129.46, 135.43, 164.67. MS: m/z 235 (M⁺), 237 (M⁺+2).

EXAMPLE 19. SYNTHESIS OF METHYL 2-CHLORO-3-METHYL-UNDEC-2-ENOATE

[0049] In accordance with the general procedure described in Example 3 above, commercial ketone was converted to methyl 2-chloro-3-methyl-undec-2-enoate and as a colorless liquid in the indicated yield for Entry 1 in Table 2.

[0050] R_(f): 0.77 (15% EtOAc in hexane). ¹H NMR (CDCI₃, 300 MHz):( Major isomer)(AK-I-208-18): δ0.88 (t, 3H, J=6.9 Hz), 1.24-1.34 (m, 10H), 1.43-1.51 (m, 2H), 2.10 (s, 3H, —CH3), 2.50-2.55(m, 2H), 3.80 (s, 3H, CO₂CH₃). ¹³C NMR (CDCI₃, 75 MHz): δ14.30, 22.66, 22.86, 28.38, 29.42, 29.58, 29.77, 32.06, 36.19, 52.65, 118.22, 151.75, 164.07. MS: m/z 246 (M⁺), 248 (M⁺+2). ¹H NMR (CDCI₃, 300 MHz):( Minor isomer)(AK-I-208-20): δ0.88 (t, 3H, J=6.9 Hz), 1.24-1.26 (m, 10H), 1.43-1.53 (m, 2H), 2.15 (s, 3H, —CH₃), 2.34-2.39 (m, 2H), 3.80 (s, 3H, CO₂CH₃). ¹³C NMR (CDCI₃, 75 MHz): δ14.29, 21.22, 22.85, 26.81, 29.38, 29.57, 29.75, 32.05, 38.10, 52.66, 117.74, 151.80, 164.07. MS: m/z 246 (M⁺), 248 (M⁺+2).

EXAMPLE 20. SYNTHESIS OF METHYL 2-CHLORO-3-PHENYL-BUT-2-ENOATE

[0051] In accordance with the general procedure described in Example 3 above, commercial acetophenone was converted to methyl 2-chloro-3-phenyl-but-2-enoate as a colorless liquid in the indicated yield for Entry 2 in Table 2.

[0052] R_(f): 0.65 (15% EtOAc in hexane). ¹H NMR (CDCI₃, 300 MHz):( Major isomer): δ2.29 (s, 3H,—CH3), 3.53 (s, 3H, CO₂CH₃), 7.14-7.17 (m, 2H), 7.30-7.40 (m, 3H). ¹³C NMR (CDCI₃, 75 MHz): δ23.84, 52.64, 120.00, 126.91, 128.21, 128.47, 141.05, 146.38, 164.69. MS: m/z 210 (M⁺), 212 (M⁺+2). ¹H NMR (CDCI₃, 300 MHz):( Minor isomer): δ2.42 (s, 3H,—CH₃), 3.87 (s, 3H, CO₂CH₃), 7.14-7.17 (m, 2H), 7.30-7.40 (m, 3H). ¹³C NMR (CDCI₃, 75 MHz): δ23.71, 52.96, 120.00, 127.16, 128.17, 128.53, 141.05, 146.38, 164.69. MS: m/z 210 (M⁺), 212 (M⁺+2).

EXAMPLE 21. SYNTHESIS OF METHYL 2-CHLORO-3-CYCLOHEX-1-ENYL-BUT-2-ENOATE

[0053] In accordance with the general procedure described in Example 3 above, commercial ketone was converted to methyl 2-chloro-3-cyclohex-1-enyl-but-2-enoate as an oil in the indicated yield for Entry 3 in Table 2.

[0054] R_(f): 0.71 (15% EtOAc in hexane). ¹H NMR (CDCI₃, 300 MHz):( Major isomer): δ1.56-1.75 (m,4H), 1.98 (s, 3H, —CH₃), 2.00-2.12 (m, 4H), 3.73 (s, 3H, CO₂CH₃), 5.43-5.46 (m, 1H). ¹H NMR (CDCI₃, 300 MHz):( Minor isomer): δ1.56-1.75 (m, 4H), 2.00-2.12 (m, 4H), 2.18 (s, 3H, —CH₃) 3.82 (s, 3H, CO₂CH₃), 5.49-5.52 (m, 1H).

EXAMPLE 22. SYNTHESIS OF METHYL 2-CHLORO-3-METHYL-5-(2,6,6-TRIMETHYL-CYCLOHEX-2-ENYL)-PENTA-2,4-DIENOATE

[0055] In accordance with the general procedure described in Example 3 above, commercial α-ionone was converted to methyl 2-chloro-3-methyl-5-(2,6,6-trimethyl-cyclohex-2-enyl)-penta-2,4-dienoate as a colorless liquid in the indicated yield for Entry 4 in Table 2.

[0056] R_(f): 0.71 (15% EtOAc in hexane). ¹H NMR (CDCI₃, 300 MHz):( Major isomer): δ0.82 (s, 3H,—CH₃), 0.91 (s, 3H,—CH₃), 1.17-1.24 (m, 2H), 1.39-1.49 (m, 1H), 1.58-1.59 (m, 3H), 2.00-2.06 (m, 2H), 2.14 (s, 3H), 2.25 (d, 1H, J=9.6 Hz), 3.83 (s, 3H, CO₂CH₃), 5.44 (br s, 1H), 5.90 (dd, 1H, J=9.6, 15.6 Hz), 7.10 (d, 1H, J=15.6 Hz). ¹³C NMR (CDCI₃, 75 MHz): δ18.22, 23.07, 23.27, 27.97, 31.78, 32.66, 52.82, 55.25, 119.82, 121.72, 129.04, 133.67, 139.16, 144.94, 164.25. MS: m/z 282 (M⁺), 284 (M⁺+2). ¹H NMR (CDCI₃, 300 MHz):( Minor isomer): δ0.82 (s, 3H, —CH₃), 0.92 (s, 3H, —CH₃), 1.18-1.27 (m, 2H), 1.40-1.51 (m, 1H), 1.56-1.61 (m, 3H), 2.00-2.08 (m, 2H), 2.22 (s, 3H), 2.31 (d, 1H, J=9.6 Hz), 3.83 (s, 3H, CO₂CH₃), 5.46 (br s, 1H), 6.00 (dd, 1H, J=9.6, 15.6 Hz), 6.77 (d, 1H, J=15.6 Hz).

EXAMPLE 23. SYNTHESIS OF METHYL 2,2-DICHLORO-3-HYDROXY-3-PHENYLPROPENOATE

[0057] In accordance with the general procedure described in Example 4 above, commercial benzaldehyde was converted to methyl 2,2-dichloro-3-hydroxy-3-phenylpropenoate in the indicated yield for Entry 1 in Table 3.

[0058] Mp 63-64° C.; ¹H NMR (CDCl₃, 300 MHz): δ3.50 (d, 1H, J=5.4 Hz), 3.85 (s, 3H), 5.38 (d, 1H, J=5.4 Hz), 7.33-7.38 (m, 3H), 7.47-7.51 (m, 2H); ¹³C NMR (CDCl₃, 75 MHz) d 54.77, 78.82, 86.14, 127.93, 128.93, 129.29, 135.55, 166.62.

EXAMPLE 24. SYNTHESIS OF METHYL 2,2-DIBROMO-3-HYDROXY-3-PHENYLPROPANOATE

[0059] In accordance with the general procedure described in Example 4 above, commercial benzaldehyde was converted to methyl 2,2-dibromo-3-hydroxy-3-phenylpropanoate in the indicated yield for Entry 2 in Table 3.

[0060] R_(f): 0.44 (30% EtOAc in hexane); mp 58-60° C.; ¹H NMR (300 MHz) δ3.45 (d, 1H, J=4.8 Hz), 3.83 (s, 3H), 5.25 (d, 1H, J=4.8 Hz), 7.27-7.32 (m, 3H), 7.49-7.53 (m, 2H); ¹³C NMR (75 MHz) δ54.97, 65.30, 78.92, 127.82, 129.30, 129.33, 136.28, 167.36; MS m/z 336 (M⁺), 338 (M⁺+2), 340 (M⁺+4); HRMS (CI, CH₄) calculated for C₁₀H₁₁Br₂O₃ (M⁺+1) m/z 336.9075, found 336.9077.

EXAMPLE 25. SYNTHESIS OF METHYL 2,2-DICHLORO-3-HYDROXY-5-PHENYLPENTANOATE

[0061] In accordance with the general procedure described in Example 4 above, commercial aliphatic aldehyde was converted to methyl 2,2-dichloro-3-hydroxy-5-phenylpentanoate in the indicated yield for Entry 3 in Table 3.

[0062] R_(f): 0.26 (20% EtOAc in hexane); mp 53-54° C.; 1H NMR (400 MHz) δ1.91-2.01 (m, 1H), 2.16-2.24 (m, 1H), 2.66 (d, 1H, J=6.4 Hz), 2.71-2.78 (m, 1H), 2.94-3.01 (m, 1H), 3.88 (s, 3H), 4.19-4.23 (m, 1H), 7.21-7.32 (m, 5H); ¹³C NMR (75 MHz) δ32.00, 32.76, 54.73, 76.68, 86.65, 126.37, 128.67, 128.72, 141.14, 166.56; MS m/z 276 (M⁺), 278 (M⁺+2), 230 (M⁺+4); HRMS (CI, CH₄) calculated for C₁₂H₁₅Cl₂O₃ (M⁺+1) m/z 277.0398, found 277.0392.

EXAMPLE 26. SYNTHESIS OF METHYL 2,2-DICHLORO-3-HYDROXY-5-PHENYLPENT-4(E)-ENOATE

[0063] In accordance with the general procedure described in Example 4 above, commercial cinnamaldehyde was converted to methyl 2,2-dichloro-3-hydroxy-5-phenylpent-4(E)-enoate in the indicated yield for Entry 4 in Table 3.

[0064] R_(f): 0.27 (20% EtOAc in hexane); mp 45-47° C.; ¹H NMR (400 MHz) δ2.90 (d, 1H, J=6.6 Hz), 3.92 (s, 3H), 4.96 (t, 1H, J=6.0 Hz), 6.35 (dd, 1H, J=15.6, 6.3 Hz), 6.82 (d, 1H, J=15.6 Hz), 7.28-7.44 (m, 5H); ¹³C NMR (75 MHz) δ54.84, 78.31, 85.88, 123.24, 127.08, 128.70, 128.88, 135.96, 136.31, 166.27; MS m/z 274 (M⁺), 276 (M⁺+2), 278 (M⁺+4); HRMS (CI, CH₄) calculated for C₁₂H₁₃Cl₂O₃ (M⁺+1) m/z 275.0242, found 275.0245.

EXAMPLE 27. SYNTHESIS OF METHYL 2,2-DICHLORO-3-(2,2-DIMETHYL-[1,3]DIOXOLAN-4(R)-YL)-3-HYDROXYPROPANOATE

[0065] In accordance with the general procedure described in Example 4 above, commercial chiral glyceraldehyde was converted to methyl 2,2-dichloro-3-(2,2-dimethyl-[1,3]dioxolan-4(R)-yl)-3-hydroxypropanoate in the indicated yield for Entry 5 in Table 3.

[0066] Major isomer: R_(f): 0.70 (50% EtOAc in hexane); mp 102-103° C.; ¹H NMR (400 MHz) δ1.30 (s, 3H), 1.35 (s, 3H), 3.09 (d, 1H, J=5.1 Hz), 3.86 (s, 3H), 4.07-4.18 (m, 2H), 4.24-4.33 (m, 2H); ¹³C NMR (75 MHz) δ25.05, 26.25, 54.61, 66.80, 75.36, 78.00, 87.05, 110.14, 165.59; HRMS (CI, CH₄) calculated for C₉H₁₅Cl₂O₅ (M⁺+1) m/z 273.0296, found 273.0297. Minor isomer: R_(f): 0.77 (50% EA in hexane); mp 34-35° C.; ¹H NMR (400 MHz) δ1.39 (s, 3H), 1.42 (s, 3H), 3.42 (d, 1H, J=9.3 Hz), 3.85-3.91 (m, 4H), 4.16-4.22 (m, 2H), 4.51-4.56 (m, 1H); ¹³C NMR (75 MHz) δ25.83, 26.17, 54.82, 68.07, 72.94, 76.18, 84.89, 110.71, 165.64; MS m/z 272 (M⁺), 274 (M⁺+2), 276 (M⁺+4); HRMS (CI, CH₄) calculated for C₉H₁₅Cl₂O₅ (M⁺+1) m/z 273.0296, found 273.0299.

EXAMPLE 28. SYNTHESIS OF ETHYL 2,2-DIFLUORO-3-HYDROXY-5-PHENYLPENTANOATE

[0067] In accordance with the general procedure described in Example 4 above, hydrocinnamaldehyde and ethyl difluorobromoacetate were converted to ethyl 2,2-difluoro-3-hydroxy-5-phenylpentanoate in the indicated yield for Entry 6 in Table 3.

[0068]¹H NMR (CDCl₃, 300 MHz): δ1.27 (t, 3H, J=7.2 Hz), 1.75-2.00 (m, 2H), 2.10 (d, 1H, J=6.9 Hz), 2.61-2.71 (m, 1H), 2.81-2.91 (m, 1H), 3.88-4.02 (m, 1H), 4.26 (q, 2H, J=7.2 Hz), 7.10-7.27 (m, 5H). ¹³C NMR (CDCl₃, 75 MHz): d 14.13, 30.91, 31.39, 63.32,70.81, 71.17, 71.50, 126.45, 128.68, 128.78, 140.94.

EXAMPLE 29. SYNTHESIS OF 2-CHLORO-3-PHENYL-PROP-2(Z)-ENAMIDE

[0069] In accordance with the general procedure described in Example 1 above, benzaldehyde and commercial 2,2,2-trichloroacetamide were converted to 2-chloro-3-phenyl-acrylamide as a colorless liquid in the indicated yield for Entry 1 in Table 4. Its spectral data were in agreement with values found in the literature. See Kruper, William J., Jr. and Emmons, Albert H., J. Org. Chem., 56: 3323-29 (1991).

EXAMPLE 30. SYNTHESIS OF 2-CHLORO-3-PHENYL-PENT-2(Z)-ENAMIDE

[0070] In accordance with the general procedure described in Example 1 above, hydrocinnamaldehyde and commercial 2,2,2-trichloroacetamide were converted to 2-chloro-3-phenyl-pent-2(Z)-enamide in the indicated yield for Entry 2 in Table 4.

[0071] R_(f): 0.20 (30% EtOAc in hexane); ¹H NMR (CDCl₃, 400 MHz) δ2.58 (q, 2H, J=7.3 Hz), 3.81 (t, 2H, J=7.3 Hz), 5.63 (bs, 1H), 6.46 (bs, 1H), 7.16-7.38 (m, 6H).

EXAMPLE 31. SYNTHESIS OF α-CHLORO-(Z)-STILBENE

[0072] In accordance with the general procedure described in Example 1 above, benzaldehyde and commercial 1,1,1-trichlorotoluene were converted to α-chloro-(Z)-stilbene in the indicated yield for Entry 3 in Table 4. Its spectral data were in agreement with values found in the literature. See Kokubo et al., J. Org. Chem., 61: 6941-46 (1996).

EXAMPLE 32. SYNTHESIS OF 1-CHLORO-1,4-DIPHENYL-1(Z)-BUTENE

[0073] In accordance with the general procedure described in Example 1 above, hydrocinnamaldehyde and commercial 1,1,1-trichlorotoluene were converted to 1-chloro-1, 4-diphenyl-I(Z)-butene in the indicated yield for Entry 4 in Table 4. Its spectral data were in agreement with values found in the literature. See Reich et al., J. Org. Chem., 43: 2402-10 (1978).

EXAMPLE 33. SYNTHESIS OF 3-CHLORO-4-PHENYL-BUT-3(Z)-EN-2-ONE

[0074] In accordance with the general procedure described in Example 1 above, benzaldehyde and commercial 1,1,1-trichloroacetone were converted to 3-Chloro-4-phenyl-but-3(Z)-en-2-one in the indicated yield for Entry 5 in Table 4. Its spectral data were in agreement with values found in the literature. See Schlosser, M. and Christmann, K. F., Synthesis, 1:38-39 (1969).

EXAMPLE 34. SYNTHESIS OF 3-CHLORO-6-PHENYL-HEX-3(Z)-EN-2-ONE

[0075] In accordance with the general procedure described in Example 1 above, hydrocinnamaldehyde and commercial 1,1,1-trichloroacetone were converted to 3-chloro-6-phenyl-hex-3(Z)-en-2-one in the indicated yield for Entry 6 in Table 4. Its spectral data were in agreement with values found in the literature. See Satoh et al., Tetrahedron Letters, 33: 1483-84 (1992).

EXAMPLE 35. SYNTHESIS OF 2-METHYL-1,3-DIPHENYL-2(E)-PROPEN-1-ONE

[0076] In accordance with the general procedure described in Example 1 above, benzaldehyde and commercial α,α,-dichloropropiophenone were converted to 2-methyl-1,3-diphenyl-2(E)-propen-1-one in the indicated yield for Entry 7 in Table 4. Its spectral data were in agreement with values found in the literature. See Aoki et al., Synlett, 10: 1071-72 (1995).

EXAMPLE 36. SYNTHESIS OF 2-METHYL-1,5-DIPHENYL-PENT-2(E)-EN-1-ONE

[0077] In accordance with the general procedure described in Example 1 above, hydrocinnamaldehyde and commercial α,β,-dichloropropiophenone were converted to 2-Methyl-1,5-diphenyl-pent-2(E)-en-1-one in the indicated yield for Entry 8 in Table 4. Its spectral data were in agreement with values found in the literature. See Ishihara et al., Synlett, 5: 597-99 (1997). 

What is claimed is:
 1. A method for the synthesis of a stereospecific tri-substituted olefin, comprising: reacting an aldehyde substrate with a halogenated compound and 4 equivalents of CrCl₂ in a solvent under an inert atmosphere for a sufficient amount of time.
 2. The method of claim 1, wherein the aldehyde substrate is selected from the group consisting of aliphatic aldehyde, aryl aldehyde, cycloaliphatic aldehyde, and heteroaromatic aldehyde.
 3. The method of claim 1, wherein the aldehyde substrate is selected from the group consisting of hydrocinnamaldehyde, cinnamaldehyde, chiral glyceraldehyde, 3-bromo-benzaldehyde, p-trifluoromethylbenzaldehyde, p-methoxybenzaldehyde, 4-benzyloxy-3-methoxy-benzaldehyde, 4-dimethylaminobenzaldehyde, and indole aldehyde.
 4. The method of claim 1, wherein the halogenated compound is a dihalogenated propionate.
 5. The method of claim 4, wherein the dihalogenated propionate is α,α-dichloropropiophenone or methyl 2,2-dichloropropionate.
 6. The method of claim 1, wherein the halogenated compound is a trihalogenated compound.
 7. The method of claim 6, wherein the trihalogenated compound is selected from the group consisting of methyl trichloroacetate, methyl tribromoacetate, 2,2,2-trichloroacetamide, 1,1,1-trichlorotoluene, 1,1,1-trichloroacetone, and ethyl dibromofluoroacetate.
 8. The method of claim 1, wherein the solvent is THF, DME, or a mixture thereof.
 9. The method of claim 1, wherein the synthesis takes place at room temperature.
 10. The method of claim 1, wherein the inert atmosphere is an argon atmosphere or a nitrogen atmosphere.
 11. The method of claim 1, wherein the amount of time is about 0.5 hours.
 12. A method for the synthesis of stereospecific tri-substituted olefins, comprising: reacting an aldehyde substrate with a halogenated compound, catalytic chromium, Mn, and TMSCl in a solvent under an inert atmosphere for a sufficient amount of time.
 13. The method of claim 12, wherein the aldehyde substrate is selected from the group consisting of aliphatic aldehyde, aryl aldehyde, cycloaliphatic aldehyde, and heteroaromatic aldehyde.
 14. The method of claim 12, wherein the aldehyde substrate is selected from the group consisting of hydrocinnamaldehyde, cinnamaldehyde, chiral glyceraldehyde, 3-bromo-benzaldehyde, p-trifluoromethylbenzaldehyde, p-methoxybenzaldehyde, 4-benzyloxy-3-methoxy-benzaldehyde, 4-dimethylaminobenzaldehyde, and indole aldehyde.
 15. The method of claim 12, wherein the halogenated compound is a dihalogenated propionate.
 16. The method of claim 15, wherein the dihalogenated propionate is α,α-dichloropropiophenone or methyl 2,2-dichloropropionate.
 17. The method of claim 12, wherein the halogenated compound is a trihalogenated compound.
 18. The method of claim 17, wherein the trihalogenated compound is selected from the group consisting of methyl trichloroacetate, methyl tribromoacetate, 2,2,2-trichloroacetamide, 1,1,1-trichlorotoluene, 1,1,1-trichloroacetone, and ethyl difluorobromoacetate.
 19. The method of claim 12, wherein the catalytic chromium is anhydrous CrCl₂ at 50 mol % concentration.
 20. The method of claim 12, wherein the solvent is THF, DME, or a mixture thereof.
 21. The method of claim 12, wherein the synthesis takes place at room temperature.
 22. The method of claim 12, wherein the inert atmosphere is an argon atmosphere or a nitrogen atmosphere.
 23. The method of claim 12, wherein the amount of time is about 12 hours.
 24. A method for the synthesis of a stereospecific tri-substituted olefin, comprising: reacting an aldehyde substrate with a dihalogenated compound, wherein the dihalogenated compound is dihalogenated propionate or a homolog of dihalogenated propionate with a longer carbon chain, and 4 equivalents of CrCl₂ in a solvent under an argon atmosphere for about 0.5 hours.
 25. A method for the synthesis of stereospecific tetra-substituted olefins, comprising: reacting a ketone substrate with a trihalogenated compound and 4 equivalents of CrCl₂ in a solvent under an inert atmosphere for a sufficient amount of time.
 26. The method of claim 25, wherein the ketone substrate is selected from the group consisting of aliphatic ketone, aromatic ketone, conjugated ketone, and hindered ketone.
 27. The method of claim 25, wherein the ketone substrate is acetophenone or α-ionone.
 28. The method of claim 25, wherein the trihalogenated compound is methyl trichloroacetate or methyl tribromoacetate.
 29. The method of claim 25, wherein the solvent is selected from the group consisting of THF, DMF, DME, and a mixture thereof.
 30. The method of claim 25, wherein the synthesis takes place at room temperature.
 31. The method of claim 25, wherein the inert atmosphere is an argon atmosphere or a nitrogen atmosphere.
 32. The method of claim 25, wherein the amount of time is about 2 hours.
 33. A method for the synthesis of dihalohydrins, comprising: reacting a substrate, wherein the substrate is an aldehyde or a ketone, and a trihalogenated compound with 2 equivalents of CrCl₂ in a solvent under an inert atmosphere for a sufficient amount of time.
 34. The method of claim 33, wherein the substrate is selected from the group consisting of aliphatic aldehyde, aryl aldehyde, cycloaliphatic aldehyde, and heteroaromatic aldehyde.
 35. The method of claim 33, wherein the trihalogenated compound is methyl trichloroacetate, methyl tribromoacetate, or ethyl difluorobromoacetate.
 36. The method of claim 33, wherein the solvent is THF, DME, or a mixture thereof.
 37. The method of claim 33, wherein the synthesis takes place at about 0° C.
 38. The method of claim 33, wherein the inert atmosphere is an argon atmosphere or a nitrogen atmosphere.
 39. The method of claim 33, wherein the amount of time is about 6 hours. 